Recording The Camera Image: The Camera obscura, at first actually a room big enough for an artist to enter, was useless until it became portable. In the seventeenth and eighteenth centuries a lens was fitted into one end of a two-foot box, and the other end was covered with a sheet of frosted or ground glass. The image cast on the ground glass by the lens could be seen outside of the camera. A perfected model, resembling the modern reflex camera, had the ground glass flush with the top of the box, the image being thrown upon it by a Mirror placed at an angle of 45°. It had the advantage that the image was not upside down, and the artist could trace it by laying thin paper over the glass.
To fill their needs, manufacturers began to introduce in the 1890s a new kind of finder: a second Camera mounted on top of the Camera with which the exposure was made. It was fitted with a lens of exactly the same focal length of the taking lens; both were focused together. On the top of the finder-camera was a ground glass the size of the negative. Within was a mirror, fixed at 45° to the lens axis, which reflected the image upwards, like the eighteenth-century Camera obscura. A collapsible hood shaded the ground glass so that the image could be seen clearly.
In his 1826 experiments Niepce was very concerned with working out a photomechanical reproduction technique as a means of recording the Camera image on a pewter plate that could be printed like a copperplate engraving. Soon after the daguerreotype process had been published, the silvered copper plates were themselves converted into intaglio plates from which impressions could be printed on paper. A satirical lithograph of 1839 by Theodore Maurisset, captioned Daguerreotypomanie, shows Alfred Donne at work with camera, aqua fortis bottle, and etcher's press.
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Photography
